JP2000068589A - Two-wavelength semiconductor laser device - Google Patents

Abstract

(57) [Problem] To provide a two-wavelength semiconductor laser device which does not lower the yield and has good mass productivity. SOLUTION: This resonator has a resonator in which at least a first electrode, a first active layer, an intermediate cladding layer, a second active layer having a composition different from the first active layer and a second active layer and a second electrode are laminated in this order. (1) the second electrode is divided into at least two parts with a predetermined width in the longitudinal direction of the resonator, or (2) a half mirror that transmits and reflects a predetermined amount of laser light generated from the resonator. The above problem is solved by a two-wavelength semiconductor laser device having a configuration including a reflecting mirror for returning a laser beam from a half mirror to a resonator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a two-wavelength semiconductor laser device. More specifically, the present invention relates to a two-wavelength semiconductor laser device that can be suitably used as a light source for reading data from an optical disk such as a DVD (digital versatile disk) and a CD.

[0002]

2. Description of the Related Art DVDs are being developed as next-generation large-capacity and portable optical recording media. As a DVD,
DVD-ROM, DVD-R, DVD-R
AM is in practical use. On the other hand, CD-ROM, CD-R
And the like are now widely used as optical recording media. Therefore, in order to use CDs continuously, it is desired to provide a DVD reproducing apparatus with a function of reading data in CDs. In particular, a CD-R that is rapidly spreading as a simple storage medium with a low unit price per storage capacity cannot read data with a near-infrared semiconductor laser device for DVD. Therefore, DV
Apart from the semiconductor laser device for D, the oscillation wavelength is about 780n
It is necessary to use a two-wavelength optical head equipped with a near-infrared semiconductor laser device of m.

[0003] The two semiconductor laser devices are not separated,
A method of mounting the semiconductor laser in one semiconductor laser package is generally known. However, this method has a problem that the interval between light emitting spots by laser light emitted from the semiconductor laser device is wide. That is, in order to collect light from two different light sources using the same lens system in the optical pickup, the interval between the light emission spots is 100 μm.
Must be: However, it is difficult to attach two semiconductor laser devices on an ordinary semiconductor laser package at a distance equal to or less than this interval.

Therefore, a two-wavelength semiconductor laser device capable of emitting laser beams of two different wavelengths from a one-chip semiconductor laser device can solve the above-described problem because two light-emitting spots can be brought close to each other. Realization is desired from the viewpoint of miniaturization of the device. In this case, CD
For applications that are compatible with all types of optical disks, such as DVDs, the two oscillation wavelengths need to be, for example, about 780 nm and about 650 nm, and the composition of the semiconductor crystal constituting the active layer needs to be changed. is there.

FIG. 15 shows a conventional example of a two-wavelength semiconductor laser device capable of emitting laser beams of the two different wavelengths.
In FIG. 15, 25 is a substrate, 26 is a current confinement layer, and 27 is V
The groove, 28 is a cladding layer, 29 is an active layer, 30 is a cladding layer, 31 is a cap layer, 32 is a cladding layer, 33 is an active layer, 34 is a cladding layer, 35 is a current confinement layer, 36 is V
The groove, 37 is a cladding layer, 38 is a cap layer, 39 is a common electrode, and 40 and 41 are electrodes. In the two-wavelength semiconductor laser device of FIG. 15, two active layers 29 and 33 having different forbidden band widths are provided above and below a cap layer 31 having a common electrode 39.

[0006] In the two-wavelength semiconductor laser device shown in FIG.
Laser beams having different wavelengths can be emitted independently.

[0007]

The two-wavelength semiconductor laser device shown in FIG. 15 has a structure in which two independent semiconductor laser devices each having an active layer are stacked in the layer direction, so that the number of manufacturing steps is large. Further, since the common electrode 39 is formed on the step of the step-like cap layer, the formation process of this electrode is complicated. Therefore, the production yield of the two-wavelength semiconductor laser device shown in FIG. 15 is reduced, and there is a problem in terms of mass productivity.

[0008]

Thus, according to the present invention, at least the first electrode, the first active layer, the intermediate cladding layer, the second active layer and the second active layer having a composition different from the first active layer in a band gap different from that of the first active layer. A two-wavelength semiconductor laser device is provided, wherein the electrodes have a resonator laminated in this order, and the second electrode is divided into at least two parts with a predetermined width in the longitudinal direction of the resonator. .

According to the above configuration, by changing the amount of current flowing through the second electrode, either the laser oscillation of the first active layer alone or the laser oscillation of the second active layer due to carriers overflowing from the first active layer. By choosing
Laser light of two wavelengths can be obtained. Further, according to the present invention, at least the first electrode, the first active layer, the intermediate cladding layer, the second active layer having a composition exhibiting a different forbidden band width from the first active layer, and the second electrode are laminated in this order. A resonator;
There is provided a two-wavelength semiconductor laser device comprising: a half mirror that transmits and reflects a predetermined amount of laser light generated from a resonator; and a reflector that returns laser light from the half mirror to the resonator.

According to the above configuration, by changing the amount of laser light returning to the resonator, either laser oscillation of the first active layer alone or laser oscillation of the second active layer due to carriers overflowing from the first active layer is achieved. By choosing
Laser light of two wavelengths can be obtained.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the two-wavelength semiconductor laser device of the present invention, of the two active layers, only the first active layer causes laser oscillation, or overflow carriers generated from the first active layer form the second active layer. A resonator is provided which leads to laser oscillation by being injected into the layer. Hereinafter, the principle of laser oscillation of the two-wavelength semiconductor laser device of the present invention will be described with reference to FIGS.
It will be described based on. In the figure, for the sake of explanation, the first active layer (active layer 1) and the second active layer (active layer 2) are p-type and n-type.
A configuration is used in which a p-type intermediate cladding layer (p-intermediate cladding) is disposed between the active layer 1 and the active layer 2, sandwiched between the p-type cladding layers (p-cladding and n-cladding). However, this configuration is for explanation, and the present invention is not limited to this configuration.

First, electrons and holes are injected into the active layer 1 by applying a voltage in the forward direction between the p-type and n-type cladding layers. If the gain due to this injection exceeds the laser oscillation threshold, the gain peak wavelength (wavelength 1) in the active layer 1
Laser oscillation occurs at the oscillation wavelength determined by
(A)). On the other hand, with the configuration described below, the threshold gain of the laser oscillator increases, and when the injection current for causing laser oscillation increases, the electrons injected into the active layer 1 overflow. In this case, even if the injection current is increased, the gain in the active layer 1 is saturated and laser oscillation does not occur. At this time, the electrons overflowing the active layer 1 flow into the adjacent active layer 2 if the disappearance due to non-radiative recombination in the intermediate cladding layer is small. The injected electrons recombine with holes existing in the active layer 2, and when the gain exceeds the laser oscillation threshold, laser oscillation occurs at an oscillation wavelength determined by the gain peak wavelength (wavelength 2) in the active layer 2. (FIG. 1 (b)).

As described above, the two-wavelength semiconductor laser device of the present invention can generate laser oscillation of two wavelengths. Hereinafter, a specific configuration of the two-wavelength semiconductor laser device of the present invention for realizing the above principle will be described. First, as a material for forming the first active layer, the intermediate cladding layer, and the second active layer, any material that can be used in the art can be used. Specifically, InGaAs
Examples include an IP-based material, an AlGaAs-based material, an InGaAsP-based material, a PbSnTe-based material, and a GaN-based material. By appropriately adjusting the composition ratio of these materials, a semiconductor laser device having a first active layer, an intermediate cladding layer, and a second active layer having desired characteristics can be obtained. Further, the first active layer and the second active layer are a multi-quantum well type in which layers made of materials having different compositions are stacked, a bulk active layer type,
It may have a structure such as a separate confinement type. Further, among the multiple quantum well types, a strained multiple quantum well type may be used.

A two-wavelength semiconductor laser device according to the present invention includes two active layers having compositions exhibiting different band gaps. Specifically, the two active layers include a combination of an AlGaInP layer (strained multiple quantum well type active layer) and an AlGaAs layer. The first active layer has a thickness of 0.01 to 0.1 μm,
Preferably, the second active layer has a thickness of 0.01 to 0.1 μm.

If the intermediate cladding layer is too thin and the two active layers are too close, when oscillating in the active layer with the wider bandgap, the other active layer becomes an absorption loss layer. As a result, waveguide loss occurs, which is not preferable.
On the other hand, if the thickness of the intermediate cladding layer is too large, the electrons overflowing the one active layer will disappear before flowing into the other active layer, and laser oscillation in the other active layer will not occur. The preferred thickness of the intermediate cladding layer is 0.05 to 0.15 μm. The intermediate cladding layer may be composed of a single layer or a plurality of layers. In the case where the layer is composed of a plurality of layers, the crystals of the layer can be easily grown.

Preferably, the intermediate cladding layer has a composition exhibiting a forbidden band width that gradually decreases from one active layer toward the other. Next, the material constituting the first electrode located below the first active layer and the second electrode located above the second active layer is not particularly limited, and any material known in the art can be used. be able to. First
The thickness of the electrode and the second electrode is preferably 0.2 to 1.0 μm.

Next, the two-wavelength semiconductor laser device of the present invention has a structure for selectively switching the laser oscillation between the first active layer and the second active layer. As such a configuration, for example, (1) a configuration in which the second electrode is divided into at least two with a predetermined width in a longitudinal direction of the resonator (2) a second electrode transmits and transmits a predetermined amount of laser light generated from the resonator There is a configuration including a half mirror that reflects light and a reflecting mirror that returns laser light from the half mirror to the resonator.

The configuration of (1) will be described with reference to FIGS. 2, 3A and 3B. First, in FIG. 2, the second electrode is divided into two electrodes (X and Y). Here, when a current is applied to both electrodes so as to have the same current density, laser oscillation occurs due to the gain of the first active layer. Next, when the current flowing through one electrode X is reduced, the waveguide below this electrode X becomes a loss region, the gain of the resonator required for laser oscillation increases, and the first active layer does not oscillate.
Therefore, when the current flowing to the second electrode Y is increased, electrons remarkably overflow from the first active layer, and the gain of the first active layer does not increase. However, the overflowed electrons flow into the second active layer, so that (2) Laser oscillation occurs due to an increase in the gain of the active layer.

Next, in FIGS. 3A and 3B, not only the second electrode but also the first active layer, the intermediate cladding layer and the second active layer are divided into two. Therefore, as a result, 2
In this configuration, two resonators are arranged close to each other in series. 2
When a current flows through both resonators, the length of the two resonators substantially becomes the resonator length. Therefore, the threshold gain of the resonator for laser oscillation is low, and laser oscillation occurs with the gain of the first active layer (FIG. 3A).

Next, when a current is applied to only one of the resonators (the left one in FIGS. 3A and 3B), the length of the resonator becomes short, and thus the resonator for laser oscillation is formed. The threshold gain increases. Therefore, when the current flowing through the resonator 1 is increased, electrons remarkably overflow from the first active layer,
Although the gain of the first active layer does not increase, the overflowed electrons flow into the second active layer, so that the gain of the second active layer increases and laser oscillation occurs (FIG. 3B).

The configuration (2) will be described with reference to FIGS. 4 (a) and 4 (b). 4A and 4B, a reflector a and a liquid crystal shutter c are provided outside the resonator d.
In FIG. 4, the half mirror is omitted. By controlling the reflecting mirror a, the amount of light reflected on the resonator d is changed. When the amount of reflected light is large, the same effect as when the reflectance of the resonator is increased occurs, and the threshold gain is reduced.
Laser oscillation occurs due to the gain of the active layer (FIG. 4A).

Next, when the amount of reflected light is small, the threshold gain increases, the gain of the second active layer increases, and laser oscillation occurs (FIG. 4B). Further, in the present invention, the above (1)
It is preferable that the first active layer has a larger bandgap than the second active layer in order to easily cause the overflow as described in (2).

With the above structure, the light emitting spots of the laser light generated from the first and second active layers can be brought close to each other, so that a plurality of optical systems are not required unlike the conventional semiconductor laser device. The semiconductor laser device of the present invention is preferably used as a light source for reading data from DVDs and CDs. Therefore, it is preferable that the first and second active layers emit a single transverse mode laser beam having an oscillation wavelength of about 650 nm and about 780 nm.

A specific configuration of the two-wavelength semiconductor laser device of the present invention will be described. First, a two-wavelength semiconductor laser device
Usually, a substrate is provided between the first electrode and the first active layer. In a semiconductor laser device, two active layers are stacked on a substrate. The first active layer, the intermediate cladding layer, and the second active layer
Usually sandwiched between cladding layers. The material forming the cladding layer is appropriately selected according to the material forming the active layer, and examples thereof include AlGaInP and AlGaAs. The cladding layer generally has a thickness of 0.8 to 1.5 μm.

Here, the cladding layer on the second active layer may be patterned into an arbitrary shape and may have a current confinement layer in order to effectively flow a current to the active layer therebelow. Further, a buffer layer may be formed between the substrate and the clad layer to improve the bonding between the two layers. The buffer layer generally has a thickness of 0.2 to 0.5 μm. Further, a cap layer for improving the bonding between the second electrode and the clad layer may be formed on the uppermost clad layer. The cap layer generally has a thickness of 0.2 to 10.0 μm.

As a specific configuration of the semiconductor laser device of the present invention, a first electrode, a substrate, a buffer layer, a clad layer,
A laminate of a first active layer, an intermediate clad layer, a second active layer, a clad layer, a cap layer, and a second electrode may be used. The substrate, the buffer layer, the clad layer, the first active layer, the intermediate clad layer, the second active layer, the clad layer, and the cap layer may have n-type or p-type conductivity.

Here, as the configuration of the above (1), (a)
A configuration in which only the second electrode is divided into two, (b) a second electrode,
A configuration in which the cap layer, the clad layer, the second active layer, the intermediate clad layer, and the first active layer are divided into two; (c) a second electrode, a cap layer, a clad layer, a second active layer, an intermediate clad layer, and a second active layer; (D) a second electrode, a cap layer, a clad layer, a second active layer, an intermediate clad layer, a first active layer, a clad layer, a buffer layer, There is a configuration in which the substrate is divided into two.

The above-mentioned resonator constituting the semiconductor laser device of the present invention comprises a first active layer, an intermediate cladding layer and a second active layer, in that order, a first electrode, a second electrode on the first active layer side.
It can be obtained by forming a second electrode on the active layer side. As a method for forming the first active layer, the intermediate cladding layer, and the second active layer, a molecular beam epitaxial method (MBE) is used.
Method, liquid phase epitaxy (LPE), metal organic chemical vapor deposition (MOCVD), and the like. Examples of a method for forming the first electrode and the second electrode include a vapor deposition method and a plating method.

In the above configuration (1), the division of the second electrode and the like can be performed by combining a known photolithography step and a known etching step. In this division, in the two-wavelength semiconductor laser device of the present invention, at least the second electrode only needs to be divided.
Unlike the conventional semiconductor laser device shown in FIG. 15, accurate etching for forming a common electrode is not required. Therefore, the manufacture of the two-wavelength semiconductor laser device of the present invention is extremely simple.

In addition, the resonator may include a buffer layer, a cladding layer, and a layer other than the first active layer, the intermediate cladding layer, and the second active layer.
When a clad layer and a cap layer are provided, the layers may be formed by molecular beam epitaxy (MBE),
Liquid phase epitaxy (LPE), metal organic vapor phase epitaxy (MOC)
VD method). The two-wavelength semiconductor laser device of the present invention can irradiate a desired position with laser light by including an optical system component. The components of the optical system are not particularly limited, and any components known in the art can be used. For example, the components of the optical system include a hologram, a diffraction grating, a condenser lens, and an objective lens.

[0031]

Embodiment 1 In the case where AlGaAs and GaInP are used as active layers, respectively.
FIG. 2 is a cross-sectional view of a two-wavelength semiconductor laser device according to the present invention.
Are shown in FIGS. 5A and 5B. FIG. 5 (a) and (b)
Is mounted on an n-GaAs substrate 1
n-GaAs buffer layer 2, n-Ga_0.5In_0.5P ba
Buffer layer 3, n- (Al_0.7Ga_0.3) _0.5In_0.5P
Cladding layer 4, AlGaInP-based strained multiple quantum well type (S
CH-MQW) first active layer 5, p- (Al_0.7Ga
_0.3)_0.5In_0.5P intermediate cladding layer 6, p-Al_0.45
Ga_0.55As intermediate cladding layer 7, p-Al_0.15Ga_0.85
As second active layer 8, p-Al_0.45Ga_0.55As clad
Layer structure in which layer 9 and p-GaAs cap layer 10 are sequentially laminated
Has structure. In this embodiment, the intermediate cladding layers 6 and 7
The thickness was 0.05 μm and 0.05 μm, respectively.

FIG. 5A is a sectional view in a direction perpendicular to the longitudinal direction of the resonator, and FIG. 5B is a sectional view in a direction parallel to the resonator. The AlGaInP-based SCH-MQW first active layer 5 has an MQW structure obtained by forming an (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P barrier layer between four non-doped Ga _0.5 In _0.5 P layers. Al _0.5 Ga _0.5 )
_It has a structure sandwiched between _0.5 In _0.5 P light guide layers.

The two-wavelength semiconductor laser device was formed as follows. First, each layer of reference numbers 2 to 10 was formed on the substrate 1 by crystal growth, for example, by the MBE method. Next, a stripe-shaped ridge waveguide was formed by etching on a portion extending from the cladding layer 9 to the cap layer 10. Next, the portion removed by etching was buried with n-GaAs14.

After that, the Au-Ge-Ni
A first electrode (backside electrode) 13 is formed on the cap layer 10 by Au.
-Zn second electrodes (surface electrodes) 11 and 12 were formed.
Here, the surface electrodes 11 and 12 formed a pattern divided into two in the longitudinal direction of the resonator for one chip of the two-wavelength semiconductor laser device. In this embodiment, the surface electrode 1
1 is 400 μm, and the length of the surface electrode 12 is 20 μm.
It was set to 0 μm. Further, the distance between the two electrodes was 30 μm.

Using the surface electrodes 11 and 12 as a mask, the substrate 1 was etched to an arbitrary depth by dry etching. By this etching, FIG.
As shown in (b), a two-wavelength semiconductor laser device including two resonators was obtained. In addition, the side surface formed by etching becomes a reflecting mirror of two resonators. The two-wavelength semiconductor laser device of this embodiment is operated as follows.

First, when a current is applied so that the surface electrodes 11 and 12 have the same current density, a composite resonator including two resonators is formed. The substantial resonator length of the composite resonator is a length obtained by adding the lengths of the two resonators. In this case, since the cavity length is long, the threshold gain of laser oscillation is low, and laser oscillation occurs due to the gain of the first active layer, and the two-wavelength semiconductor laser device oscillates at a wavelength of 650 nm (FIG. 6A).

Next, for example, when no current is applied to the surface electrode 12, laser oscillation occurs only in the resonator 1. In this case, since the cavity length becomes shorter, the threshold gain for laser oscillation increases. Therefore, in order to perform laser oscillation, it is necessary to increase the injection current more than in the above case. When the injection current to the surface electrode 11 is increased to increase the injection current, the overflow of electrons from the first active layer becomes remarkable, and the gain of the first active layer no longer increases. However, when the overflowed electrons flow into the second active layer, the gain of this layer increases and laser oscillation occurs, and the two-wavelength semiconductor laser device oscillates at a wavelength of 780 nm (FIG. 6B).

Embodiment 2 FIGS. 7A and 7B are cross-sectional views of a two-wavelength semiconductor laser device according to the present invention, in which AlGaAs and GaInP are used as active layers, respectively. FIGS. 7A and 7B
In the two-wavelength semiconductor laser device, an n-GaAs buffer layer 2 and an n-Al _0.45 Ga _0.55 As are formed on an n-GaAs substrate 1.
Cladding layer 15, p-Al _0.15 Ga _0.85 As first active layer 16, p-Al _0.35 Ga _0.65 As intermediate cladding layer 17,
AlGaInP-based SCH-MQW second active layer 18, p-
_{(Al 0.7 Ga 0.3) 0.5 In} 0. 5 P cladding layer 19,
p-GaInP intermediate layer 20, p-GaAs cap layer 1
0 are sequentially laminated. AlGaInP-based S
The CH-MQW second active layer 18 had the same structure as that of the first embodiment.

The two-wavelength semiconductor laser device was formed as follows. First, layers 2 to 10 are formed on the substrate 1 by crystal growth, for example, by the MOCVD method. Next, from the cladding layer 19 to the cap layer 10
A stripe-shaped ridge waveguide was formed by etching over a portion straddling the ridge waveguide. Next, the portion removed by etching was buried with n-GaAs 14 by MOCVD.

Thereafter, in the same manner as in the first embodiment, an Au-Ge-Ni first electrode (back surface electrode) 13 is provided on the back surface of the substrate 1.
Au-Zn second electrode (surface electrode) 1 on the cap layer 10
1 and 12 were formed. Using the front electrodes 11 and 12 as a mask, the back electrode 13 is formed by dry etching.
Was etched until was exposed. By this etching, a two-wavelength semiconductor laser device including two resonators as shown in FIGS. 7A and 7B was obtained.

FIG. 7A is a sectional view in a direction perpendicular to the longitudinal direction of the resonator, and FIG. 7B is a sectional view in a direction parallel to the resonator. When the obtained two-wavelength semiconductor laser device is operated in the same manner as in Example 1, it oscillates at a wavelength of 780 nm when a current is applied to the two surface electrodes, and 650 nm when an electric current is applied to the surface electrode 11. Oscillates at In this embodiment, the height of the barrier is reduced by lowering the Al mixed crystal ratio of the intermediate cladding layer in order to easily cause the overflow of electrons from the first active layer.

Embodiment 3 In the case where AlGaAs and GaInP are used as active layers, respectively.
FIG. 2 is a cross-sectional view of a two-wavelength semiconductor laser device according to the present invention.
Are shown in FIGS. 8A and 8B. FIGS. 8A and 8B
Is mounted on an n-GaAs substrate 1
n-GaAs buffer layer 2, n-Ga_0.5In_0.5P ba
Buffer layer 3, n- (Al_0.7Ga_0.3) _0.5In_0.5P
Clad layer 4, AlGaInP-based SCH-MQW first active
Layer 5, p- (Al_0.7Ga_0.3)_0.5In_0.5P middle
Clad layer 6, p-Al_0.45Ga _0.55As intermediate cladding
Layer 7, p-Al_0.15Ga_0.85As second active layer 8, pA
l _0.45Ga_0.55As clad layer 9, p-GaAs cap
And has a layer structure in which the pump layers 10 are sequentially laminated. AlGaIn
The P-based SCH-MQW first active layer 5 is the same as in the first embodiment.
Structured.

The two-wavelength semiconductor laser device was formed as follows. First, each layer of reference numbers 2 to 10 was formed on the substrate 1 by crystal growth, for example, by the MBE method. Next, a stripe-shaped ridge waveguide was formed by etching on a portion extending from the cladding layer 9 to the cap layer 10. Next, the portion removed by etching was buried with n-GaAs14.

Thereafter, the Au-Ge-Ni
A first electrode (backside electrode) 13 is formed on the cap layer 10 by Au.
-Zn second electrodes (surface electrodes) 11 and 12 were formed.
Here, the surface electrodes 11 and 12 formed a pattern divided into two in the longitudinal direction of the resonator for one chip of the two-wavelength semiconductor laser device. In this embodiment, the surface electrode 1
1 is 100 μm, and the length of the surface electrode 12 is 50 μm.
It was set to 0 μm. Further, the distance between the two electrodes was 30 μm.

FIG. 8A is a sectional view in a direction perpendicular to the longitudinal direction of the resonator, and FIG. 8B is a sectional view in a direction parallel to the resonator. The two-wavelength semiconductor laser device of this embodiment is operated as follows. First, when a current is applied so that the surface electrodes 11 and 12 have the same current density, laser oscillation occurs due to the gain of the first active layer, and the two-wavelength semiconductor laser device oscillates at a wavelength of 650 nm (FIG. 9A). .

Next, for example, when the injection current to the surface electrode 11 is reduced, the waveguide below this electrode becomes a loss area, the gain of the resonator required for laser oscillation increases, and laser oscillation stops. When the injection current to the surface electrode 12 is increased, the overflow of electrons from the first active layer becomes remarkable, and the gain of the first active layer no longer increases. However,
When the overflowed electrons flow into the second active layer, the gain of this layer increases and laser oscillation occurs, and the two-wavelength semiconductor laser device oscillates at a wavelength of 780 nm (FIG. 9).
(B)).

Embodiment 4 AlGaAs and GaInP as Active Layers
FIG. 2 is a cross-sectional view of a two-wavelength semiconductor laser device according to the present invention.
Are shown in FIGS. 10A and 10B. FIG. 10 (a) and
The two-wavelength semiconductor laser device of (b) is an n-GaAs substrate
N-GaAs buffer layer 2, n-Al_0.45Ga
_0.55As clad layer 15, p-Al_0.15Ga _0.85As No.
1 active layer 16, p-Al_0.3Ga_0.7As intermediate cladding
Layer 17, AlGaInP-based SCH-MQW second active layer 1
8, p- (Al_0.7Ga_0.3)_0.5In_0.5P clad
Layer 19, p-GaInP intermediate layer 20, p-GaAs capacitor
It has a layer structure in which a top layer 10 is sequentially laminated. AlGaI
The nP-based SCH-MQW second active layer 18 has the structure of the first embodiment.
And the same structure.

The two-wavelength semiconductor laser device was formed as follows. First, layers 2 to 10 are formed on the substrate 1 by crystal growth, for example, by the MOCVD method. Next, from the cladding layer 19 to the cap layer 10
A stripe-shaped ridge waveguide was formed by etching over a portion straddling the ridge waveguide. Next, the portion removed by etching was buried with n-GaAs 14 by MOCVD.

Thereafter, the Au-Ge-Ni first electrode (back surface electrode) 13 is provided on the back surface of the substrate 1 in the same manner as in the third embodiment.
Au-Zn second electrode (surface electrode) 1 on the cap layer 10
1 and 12 were formed. Using the surface electrodes 11 and 12 as a mask, n-GaAs is formed by dry etching.
The cap layer 10 was etched until 14 was exposed.
The reason for etching the cap layer 10 is that the cap layer 1
This is for suppressing the spread of the current at 0 and clarifying the effect of dividing the electrodes.

FIG. 10A is a sectional view in a direction perpendicular to the longitudinal direction of the resonator, and FIG. 10B is a sectional view in a direction parallel to the longitudinal direction. When the obtained two-wavelength semiconductor laser device is operated in the same manner as in Example 3, when a current is applied to the two surface electrodes, the laser oscillates at a wavelength of 780 nm, and when the injection current to the surface electrode 11 is reduced, It oscillates at a wavelength of 650 nm. In this embodiment, in order to easily cause overflow of electrons from the first active layer, the A of the intermediate cladding layer is used.
The height of the barrier is reduced by lowering the mixed crystal ratio.

Embodiment 5 AlGaAs and GaInP as Active Layers
FIG. 2 is a cross-sectional view of a two-wavelength semiconductor laser device according to the present invention.
Is shown in FIG. The two-wavelength semiconductor laser device of FIG.
On an n-GaAs substrate 1, an n-GaAs buffer layer 2, n
-Ga_0.5In _0.5P buffer layer 3, n- (Al_0.7G
a_0.3)_0.5In_0.5P cladding layer 4, AlGaInP
SCH-MQW first active layer 5, p- (Al_0.7Ga
_0.3)_0.5In_0.5P intermediate cladding layer 6, p-Al_0.45
Ga_0.55As intermediate cladding layer 7, p-Al_0.15Ga_0.85
As second active layer 8, p-Al_0.45Ga_0.55As clad
Layer structure in which layer 9 and p-GaAs cap layer 10 are sequentially laminated
Has structure. AlGaInP-based SCH-MQW first activity
The layer 5 had the same structure as that of the first embodiment.

The two-wavelength semiconductor laser device was formed as follows. First, each layer of reference numbers 2 to 10 was formed on the substrate 1 by crystal growth, for example, by the MBE method. Next, a stripe-shaped ridge waveguide was formed by etching on a portion extending from the cladding layer 9 to the cap layer 10. Next, the portion removed by etching was buried with n-GaAs14.

After that, the Au-Ge-Ni
A first electrode (backside electrode) 13 is formed on the cap layer 10 by Au.
-A second Zn electrode (surface electrode) 11 was formed. As shown in FIG. 12, the two-wavelength semiconductor laser device of this example was mounted on a package in combination with an external reflecting mirror a, a half mirror b, and a liquid crystal shutter c. In FIG. 12, e means a light receiver.

The two-wavelength semiconductor laser device of this embodiment is operated as follows. First, when the liquid crystal shutter c is opened and there is reflected light from the external reflecting mirror a to the laser resonator d, the threshold gain for laser oscillation of the resonator is low, and the gain of the first active layer is low. Causes laser oscillation, and the two-wavelength semiconductor laser device oscillates at a wavelength of 650 nm (FIG. 13A).

Next, when the liquid crystal shutter c is closed and there is no reflected light from the external reflecting mirror a to the laser resonator d, the gain of the resonator required for laser oscillation increases, and laser oscillation occurs. Disappears. When the injection current to the surface electrode 11 is increased, the overflow of electrons from the first active layer becomes remarkable, and the gain of the first active layer no longer increases. However, when the overflowed electrons flow into the second active layer, the gain of this layer increases and laser oscillation occurs.
The two-wavelength semiconductor laser device oscillates at a wavelength of 780 nm (FIG. 13B).

Embodiment 6 In the case where AlGaAs and GaInP are used as active layers, respectively.
FIG. 2 is a cross-sectional view of a two-wavelength semiconductor laser device according to the present invention.
Is shown in FIG. The two-wavelength semiconductor laser device of FIG.
On an n-GaAs substrate 1, an n-GaAs buffer layer 2, n
-Al_0.45Ga _0.55As clad layer 19, p-Al_0.15
Ga_0.85As first active layer 20, p-AlGaAs intermediate layer
Lad layer 21, AlGaInP-based SCH-MQW second active
Layer 22, p- (Al_0.7Ga_0.3)_0.5In_0.5P
Lad layer 23, p-GaInP intermediate layer 24, p-GaAs
It has a layer structure in which s cap layers 10 are sequentially laminated. Al
The GaInP-based SCH-MQW second active layer 22 is described in the embodiment.
The structure was the same as that of Example 1.

In this embodiment, in order to easily cause the overflow of electrons from the first active layer, the Al mixed crystal ratio of the intermediate cladding layer is increased from 0.45 from the first active layer toward the second active layer. By gradually lowering the barrier height to 0.30, the height of the barrier is reduced. The two-wavelength semiconductor laser device was formed as follows.

First, layers 19 to 24 and 10 were formed on the substrate 1 by crystal growth, for example, by MOCVD. Next, a stripe-shaped ridge waveguide was formed by etching on a portion extending from the cladding layer 23 to the cap layer 10. Next, the portion removed by etching is n-GaAs1 by MOCVD.
Embedded with 3.

Thereafter, in the same manner as in the third embodiment, the Au-Ge-Ni first electrode (back surface electrode) 13 is provided on the back surface of the substrate 1.
Au-Zn second electrode (surface electrode) 1 on the cap layer 10
1 was formed. The two-wavelength semiconductor laser device of this embodiment is
In the same manner as in Example 5, as shown in FIG. 12, an external reflecting mirror a, a half mirror b, and a liquid crystal shutter c were combined and mounted on a package.

The obtained two-wavelength semiconductor laser device is operated in the same manner as in the fifth embodiment.
Oscillates at 80 nm, and when there is no reflected light, the wavelength is 650 n
It oscillates at m.

[0061]

The two-wavelength semiconductor laser device of the present invention has two active layers having different band gaps from each other, and can select laser beams having two different oscillation wavelengths. Further, the interval between the light emitting spots of the laser beams of the respective wavelengths can be made close to 10 μm or less.

Further, the two-wavelength semiconductor laser device of the present invention has a simple structure, so that the yield is higher than before and it is suitable for mass production. In particular, if the two-wavelength semiconductor laser device of the present invention is used for an optical pickup, it is possible to provide a small-sized optical head compatible with all DVD and CD optical disks.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the principle of laser oscillation of a two-wavelength semiconductor laser device according to the present invention.

FIG. 2 is a diagram for explaining control means of the two-wavelength semiconductor laser device of the present invention.

FIG. 3 is a diagram for explaining control means of the two-wavelength semiconductor laser device of the present invention.

FIG. 4 is a diagram for explaining control means of the two-wavelength semiconductor laser device of the present invention.

FIG. 5 is a schematic cross-sectional view of the two-wavelength semiconductor laser device according to the first embodiment.

FIG. 6 is a graph showing a change in gain spectrum due to a difference in resonator length of the two-wavelength semiconductor laser device of Example 1.

FIG. 7 is a schematic sectional view of a two-wavelength semiconductor laser device according to a second embodiment.

FIG. 8 is a schematic sectional view of a two-wavelength semiconductor laser device according to a third embodiment.

FIG. 9 is a graph showing a change in gain spectrum due to a difference in a loss of a resonator of the two-wavelength semiconductor laser device of Example 3.

FIG. 10 is a schematic sectional view of a two-wavelength semiconductor laser device according to a fourth embodiment.

FIG. 11 is a schematic sectional view of a two-wavelength semiconductor laser device according to a fifth embodiment.

FIG. 12 is an example of mounting a two-wavelength semiconductor laser device of Example 5 on a package.

FIG. 13 is a graph showing a change in gain spectrum due to a difference in reflectance of a resonator of the two-wavelength semiconductor laser device of Example 5.

FIG. 14 is a schematic sectional view of a two-wavelength semiconductor laser device according to a sixth embodiment.

FIG. 15 is a schematic sectional view of a conventional two-wavelength semiconductor laser device.

[Explanation of symbols]

1,25 substrate 2,3 buffer layer 4,9,15,19,28,30,32,34,37
Cladding layer 5, 16, 20 First active layer 6, 7, 17, 21 Intermediate cladding layer 8, 18, 22 Second active layer 10 Cap layer 11, 12 Front surface electrode 13 Back surface electrode 14 n-GaAs 20, 24 Middle layer 26, 35 Current confinement layer 27, 36 V groove 29, 33 Active layer 31, 38 Cap layer 39 Common electrode X, Y, 40, 41 Electrode a External reflector b Half mirror c Liquid crystal shutter d Laser resonator e Receiver

Claims (7)

[Claims] 1. A resonator comprising at least a first electrode, a first active layer, an intermediate cladding layer, a second active layer having a composition different from that of the first active layer and a second active layer and a second electrode laminated in this order. A two-wavelength semiconductor laser device, wherein the second electrode is divided into at least two with a predetermined width in the longitudinal direction of the resonator. 2. The device according to claim 1, wherein the first active layer, the intermediate cladding layer, the second active layer, and the second electrode are divided into at least two parts with a predetermined width in the longitudinal direction of the resonator. 3. A substrate having a substrate between a first electrode and a first active layer, wherein the substrate, the first active layer, the intermediate cladding layer, the second active layer, and the second electrode are arranged in a predetermined direction in a longitudinal direction of the resonator. 2. The device of claim 1, wherein the device is divided into at least two in width. 4. A resonator in which at least a first electrode, a first active layer, an intermediate cladding layer, a second active layer having a composition exhibiting a bandgap different from that of the first active layer and a second electrode are stacked in this order. A two-wavelength semiconductor laser device comprising: a half mirror for transmitting and reflecting a predetermined amount of laser light generated from the resonator; and a reflecting mirror for returning laser light from the half mirror to the resonator. 5. The device according to claim 1, wherein the second active layer has a larger bandgap than the first active layer. 6. The first active layer and the second active layer are formed of AlGa.
6. The device according to claim 1, comprising an As layer and an AlGaInP layer. 7. An intermediate cladding layer is formed between the first active layer and the second active layer.
The device according to any one of claims 1 to 6, wherein the composition has a forbidden band width gradually decreasing toward the active layer.